Crop drying oil burner

ABSTRACT

This burner includes a cylindrical combustion chamber, and means which blow air through the chamber. A circular opening in the chamber&#39;&#39;s front plate and a plurality of peripheral apertures and radial slits in the chamber&#39;&#39;s rear plate allow air to pass through the chamber. Pitched blades adjacent the slits cause this moving air to form a vortex within the chamber, and when oil is injected into the vortex and ignited, a clean, smoke-free flame shoots out the circular opening. If a centrifugal fan is used as the air blowing means, the chamber is ideally located in the quiet zone opposite the fan&#39;&#39;s hub. In this instance, air intercepting and directing means collect some air from the peripheral air stream generated by the fan, and direct this intercepted air into the chamber.

United States Patent Inventors Appl. No. Filed Patented Assignee CROPDRYING OIL BURNER 12 Claims, 7 Drawing Figs.

u.s.c1 263/19, 431/11s,431/17s,431/1s3 1m.c1 F24h 3/02 FieldofSearch431/115, 116, 158, 174, 175, 182, 183; 263/19 Primary ExaminerEdward G.Favors Att0rneysArthur G. Gilkes, William T. McClain and John J.

Connors ABSTRACT: This burner includes a cylindrical combustion chamber,and means which blow air through the chamber. A circular opening in thechambers front plate and a plurality of peripheral apertures and radialslits in the chambers rear plate allow air to pass through the chamber.Pitched blades adjacent the slits cause this moving air to form a vortexwithin the chamber, and when oil is injected into the vortex andignited, a clean, smoke-free flame shoots out the circular opening. If acentrifugal fan is used as the air blowing means, the chamber is ideallylocated in the quiet zone opposite the fan s hub. In this instance, airintercepting and directing means collect some air from the peripheralair stream generated by the fan, and direct this intercepted air intothe chamber.

I I I 16 'PATEN-TEDIFEB len 3.1561; 74

I sum 5 or 5 07 TOP V5) .7147 20 122 pmafia aw CROP DRYING OIL BURNERBACKGROUND OF THE INVENTION Crop drying is potentially one of thelargest markets for fuel oil, yet it remains virtually untapped: thereason, incomplete, smoky oil combustion which impairs the taste, odor,and color of the grain being dried. Grain may be dried using either adirect-fired or indirect-fired burner. In the latter case, air cominginto contact with the grain is heated indirectly so that it neverintermingles with the flame of the burner. This is a very expensivesystem. The direct-fired burner is a much more economic system, but fuelcombustion .must be complete so that taste, odor, and color contaminantsare not fed into the grain. Most conventional crop dryers employdirect-fired burners fueled by clean burning liquid petroleum gas (LPG)or natural gas. Because fuel oil generally costs considerably less perB.t.u. than LPG, and because of the scarcity of LPG and natural gas insome areas, direct-fired crop drying oil burners would be highlydesirable. But to date most, if not all, attempts to design an oilburner suitable for direct-fired crop drying have resulted in failurebecause smoky oil combustion could not be eliminated.

Three major factors govern smoke-free oil combustion: the oil-air ratio,the temperature inside the burners combustion chamber, particularly thetemperature of the inner wall of the combustion chamber, and the mannerin which the air flows through the chamber. Sufficient air must alwaysbe present to insure complete combustion of the oil. Insufficient aircauses smoking. However if too much air is blown through the chamber,the inner wall of the chamber cools, and when the burner is shutdown,any oil remaining in the chamber vaporizes slowly, causing smokyafterbuming. Thus, the proper balance of air and oil must be maintainedto guarantee smoke-free combustion and to avoid excessive cooling of thechamber. Moreover, even when the oil-air ratio and chamber temperatureare optimized, smoky combustion products still form. We have found thatby restricting the air flow at the front of the chamber, thesecombustion products can be recirculated within the chamber until theyare completely consumed.

BRIEF DESCRIPTION OF THE INVENTION We have invented an oil burner whichprovides clean, smoke-free burning at startup, throughout prolongedoperation, and at shutdown. This 'bumer has many excellent attributes.The most outstanding is,of course, that it provides a clean, smoke-freeflame. But it is also easy to build, inexpensive to operate andmaintain, provides reliable, trouble-free service, and can readily bedesigned to provide a heat output of from about one million to about tenmillion B.t.u.s per hour in a 30-60 m.p.h. blast of air. Such a highheat output burner is exceptionally well suited for use in mostconventional crop dryers.

Our oil burner, in common with most oil burners, includes a combustionchamber having rear and front openings for allowing air to enter andexit, means adjacent the rear opening for moving air rapidly through thechamber, and means for feeding oil into the chamber and igniting theoil-air mixture. What characterizes our invention is the way in whichair moves through our burner. We have designed our burner so that thereare three principal air currents within the chamber: l a vortex ofspinning air in the central portion of the chamber, (2) a laminar-likestream near the inner wall of the chamber which surrounds the vortex ofthe spinning air and flows out the front opening, and (3) arecirculating air stream flowing counter to the laminarlike air stream.The vortex of spinning air intimately mixes oil and air; the laminarlikeair stream aids in confining this oil-air mixture to the central portionof the chamber and in keeping oil off the chambers inner wall; and therecirculating air stream aids in keeping the fuel oil particles withinthe chamber until they are completely vaporized.

The size and shape of the chamber, especially the size and shape of thefront and rear openings, are also important. By regulating the shape anddimensions of the chamber and openings, we can balance the oil-air ratioand control, at least partially, the chambers temperature. The chambermust have a large enough volume to accommodate the oil being fed intoit, and the openings must be sufficiently expansive to permit entry ofenough air, and thereby guarantee smoke-free oil combustion, andsufficiently restrictive to prohibit entry of excess air, and therebyguarantee against undue cooling of the chamber with attendant smokyshutdown.

For a particular set of parameters, the proper chamber size and properopening dimensions can be determined empiri cally. For example, mostmoist grains can be dried if the burner is fired at a rate between 1 and45 gallons per hour. Using a conventional centrifugal fan whichgenerates a pressure between about 2 and about 4 inches of water, air isblown through the chamber of the burner at a rate of from about 20 to900 c.f.m. The grain ordinarily presents a back pressure of between Iand 3 inches of water, and the air temperature generally ranges between0 and F. Under these conditions, the dimensions of the front and rearchamber openings are adjusted so that temperature of the chambers innerwall remains above about l400 F., preferably in the range of from about1600* F. to about 2000 F. If the chamber is insulated, this temperatureis more easily maintained. If oil particles strike this hot inner wall,they evaporate immediately and burn completely with a minimum of cokeand smoke formation.

In accordance with a more detailed feature of our invention, thecombustion chamber is a hollow cylinder having a front and rear plate.Preferably the chamber is made of a heat resistant metal alloy or castiron wrapped in an insulating material or a nonporous ceramic or likeheat resistant-insulating material. In the chambers front plate, thereis a centrally located, circular outlet which has a diameter equal tofrom about one-third to about two-thirds, preferably about onehalf, thediameter of the chamber. The ratio of chamber diameter to chamber lengthto outlet diameter is about 2:23:l, preferably about 212.521. Althoughthese ratios can vary somewhat, if they vary too greatly, smoky burningresults.

In the chambers rear plate, there are a plurality of apertures adjacentthe plates periphery, and a plurality of radially extending slitsbetween the plates periphery and center. As the air enters the chamber,pitched blades, mounted adjacent the slits, swirl the air about to forma vortex within the chamber. Oil feeding and igniting means, centrallymounted within the rear plate, inject oil into this vortex and set theoilair mixture afire, so that the forward two-thirds of the chamber isfilled with flame that shoots out the outlet inthe front plate. Theapertures direct air entering the chamber along a course adjacent thechambers inner wall so that the swirling mass of oil and air tends to beconfined to the central portion of the chamber. Some air strikes theinside of the front plate and recirculates, carrying unvaporized oil andcombustion products with it back into the vortex.

Preferably the oil feeding and igniting means includes a shield and, aplurality of nozzles. The shield is a frustoconical element whichsurrounds the oil feeding and igniting means and prevents overheating ofthese means and buildup thereon of carbon or the like. The spray fromthe noules is aimed at the center of the chamber. This reduces theamount of oil thrown against the inner walls of the chamber, andconsequently, also reduces the possibility of smoking. The feeding ofoil into one or more of the nozzles may be controlled by a thermostatlocated in the crop dryer.

In designing an oil burner for crop drying, we also encountered anotherproblem. Conventional crop dryers employ large radial or backwardpitched centrifugal fans which push air away from the fans but towardsthe fan's housing. The combustion chamber of a burner is ideally locatedin the quiet zone opposite the hub, but since there is little or no airflow through this zone, smoky oil combustion will occur unless measuresare taken to introduce more air into the chamber. We overcome thisproblem by mounting, between the fan and chamber, means which interceptair coming from the peripheral edge of the fan and which direct thisintercepted air into the chamber.

In accordance with this feature of our invention, we employ a revolvingfan having a plurality of vanes extending radially from the fan's hub.The spinning vanes force air away from the hub, towards the periphery ofthe fan, and generate a high velocity air stream which flows away fromthe fan along a course that intersects the plane through which the fanrevolves. A combustion chamber, including oil feeding and igniting meansand having an air passageway, is aligned opposite the hub on the sameside of the fan as the air stream, but out of said air stream. Aplurality of conduits positioned between the chamber and fan collectsome air from the stream and feed this air into the passageway. Thus,the chamber receives an adequate supply of air.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of aconventional crop dryer employing the oil burner of our invention.

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1.

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 2.

FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 2.

FIG. 6 is a cross-sectional view taken along line 6-6 of FIGv 2.

FIG. 7 is an enlarged perspective view of one of the slits in the rearplate shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 depicts burner 10 of ourinvention mounted in rear wall 12 of portable crop dryer 14. A highvelocity hot air stream coming from burner I0 dries moist grain 16 beingcontinually fed into hopper 24 at the top of drycr l4. Simultaneously,dry grain 18 is withdrawn from the bottom of dryer l4. Auger 20uniformly distributes grain 16 over the top of dryer 14, and under theguidance of inclined walls 26 and 28, and under the influence ofgravity, this grain l6 flows over pcrforated roof 30 of internal housing32, between perforated sidewalls 34 of internal housing 32 andperforated sidewalls 36 of external housing 40, sidewalls then intopassageways 42 (only one shown) on opposite sides of dryer 14. Partition46 divides internal housing 32 into upper section 48 and lower section50. Burner 10 blows hot air through the upper section 48 and out roof 30and sidewalls 34. This hot air, moving countercurrent to the flow ofgrain 16, dries the grain and then leaves dryer 14. At the same time,cool air fan 52 blows cool air through lower section 50 and then outperforated sidewalls 34. Consequently, when grain 16 arrives atpassageways 42, it is both dry and cool. Augers 54 (only one shown)within passageways 42, feed dried grain 18 out ports 58 and 60 and intoa suitable storage bin (not shown).

Burner 10, best shown in FIG. 2, has three major components: air movingassembly 62, combustion chamber 64 positioned in front of the air.rnoving assembly, and fuel injecting and igniting assembly 66 attachedto the chamber. Assembly 62 blows air into chamber 64, and assembly 66simultaneously sprays oil into chamber 64 and ignites the oil-airmixture.

Air moving assembly 62 includes conventional centrifugal fan 68 andspiderlike subassembly 70 (FIGS. 2-4) which serves as air interceptingand directing means. As the fans power shaft 72 turns, vanes 74,bristling forth from the fan s hub 76 and almost touching the fan'shousing 78, bite into the air and throw air against housing 78. Housing78 trains this speeding air along a course indicated by arrows a.Because of the manner in which fan 68 operates, there is little or nomovement of air outwardly from hub 76v As mentioned, this poses aproblem, Namely, chamber 64, ideally located opposite hub 76, will notreceive enough air to guarantee smokefree combustion unless correctivemeasures are adopted. Subassembly 70 provides the necessary correctivemeasures.

More specifically, subassembly 70 catches a portion of the air comingfrom the periphery of fan 68 and feeds it into chamber 64. Thissubassembly 70 includes compartment 80 and radial air ducts 82 whichmerge in the compartment. Each duct 82 has an open ended elbow 84twisted so that its opening 86 lines up with the direction of flow ofthe high velocity air stream indicated by arrows a. Each duct 82 alsohas an open ended arm 88 coupled to compartment 80 so that its opening90 (FIG. 2) allows air to enter the compartment. Air flows through ducts82 into compartment 80 and then out the compartments exit 92 intochamber 64, which is attached to the compartment.

Chamber 64 is preferably a hollow, cylinder 96 made, for example, of anonporous ceramic or other suitable heat resistant, insulating material.Front plate 98, integral with chamber 64, has circular opening 100therein which has its center coincident with the longitudinal axis ofchamber 64. Circular opening 100 has a diameter (11,) equal to aboutonehalf the chambers diameter (11,). The Chamber's length (1,) isslightly greater than the chambers diameter ((1,).

As best illustrated in FIGS. 5-7, the chambers rear plate 102 has aplurality of apertures 106 adjacent the plates periphery and a pluralityof radial slits 108 between the plates periphery and center; Each slit108 has a length (1,) equal to about one-sixth the diameter (11,) ofchamber 64, and near each slit 108 is a blade I10 also having a length(I,,)-equal to about one-sixth the diameter ((1,) of chamber 64. Blades110 are pitched at an angle of about 45 relative to the back 112 (FIG.7) of rear plate 102, and they cover about one-half of the slit'sopening. Apertures 106 and slits 108 are designed so that the ratio ofair entering chamber 64 through the apertures to air entering chamber 64through slits 108 is about l:l.Air from subassembly 70 rushes intochamber 64 via apertures I06 and slits 108, and blades I10 chop intothis blast of air, causing it to swirl about violently and form a vortexwithin chamber 64. Air passing through apertures 106 confines thisvortex within the central portion of chamber 64, and aids in keeping oiloff inner wall 104 of chamber 64. Most of the air entering chamber 64gushes from opening 100, but some strikes the inside of front plate 98and recirculates. This recirculating air aids in keeping oil particleswithin chamber 64 until they are completely vaporized. We prefer to haveplate 98 at a right angle relative wall 104 in order to maximizerecirculation.

Fuel injecting and igniting subassembly 66, located securely within rearplate 102 at the plates center, includes support block 114 which carriesnozzles 116, 118, and 120, and electrodes I22 and 124. Fuel line 126,which has three branches 128, I30, and 132, leading respectively intonozzles 116, 118, and 120, feeds oil into these nozzles. Nozzles 116,118, and then spray oil into the vortex. Desirably, nozzles 116, I18,and 120 are tilted slightly inwardly so that a line passing throughtheir respective orifices intersects the center of chamber 64. Aimingnozzles 116, 118, and 120 in this manner reduces the amount of oilspewed against inside wall 104 (FIG. 2) of chamber 64, and consequently,reduces the likelihood of smoking. A high voltage established betweenelectrodes 122 and 124 causes a spark to flash across the gap betweenthem. This spark ignites the whirlpool of oil and air in chamber 64,filling forward end of chamber 64 with flame 142 that shoots out opening100.

We have found that in some instances recirculating air carries with itcarbon that is deposited on porcelain holders 143 for electrodes I22 and124. This shorts out electrodes 122 and 124. By providing shield meanswhich surround fuel injecting and igniting assembly 66, this problem isavoided. The preferred form of shield means is a frustoconical member144 welded to rear plate 102. The size of this memhers mouth 146 iscarefully adjusted so that member 144 does not interfere with the oilspray, but will still protect assembly 66 against carbon deposits.Member 144 also helps maintain assembly 66 at a reasonably lowtemperature, so that this assembly is not damaged by overheating.

In operation. oil is fed into nozzle 120 continuously at a predeterminedrate, whereas oil is fed to nozzles 116 and 118 intermittently under thecontrol of thermostats 148 and 150 (FIG. I) located in crop dryer l4.Thermostats 148 and 150 control the operation of valves 152 and 154(FIG. 4), which are respectively located in branch lines 128 and 130.When the temperature of grain l6 in contact with thermostats 148 and 150falls below a predetermined level, the thermostats activated solenoids(not shown) which open valve 152 or valve 154 or both.

We have built three different size burners generally in accordance withthe above disclosed design. Each burner provides smoke-free combustion;each burner employs a conventional, high velocity fan which generates aforward air pressure against the rear plate of about 3 inches of water;and each burner is used to dry crops which present a back pressure ofabout 2 inches of water (the back pressure normally encountered indrying crops). These burners meet the following specifications:

Burner 1 Burner 2 Burner 3 Chamber length, 1 inches- 8 10. 5 15. 5Chamber diameter, dc, inches 6 8 12 Opening diameter, d, inches 3. 25 4.3 6. 5 Total aperture opening, square 2 2. 9 4. 8 Total slit opening,square inches 2 2. 9 4. 8 Total open area in rear plate, square inches 45. 8 9. 6 Air velocity through chamber, cubic feet per minute -100 -23O-500 Temperature of chambers inner wall,

-1, 600 -1, 600 -1, 600 Firing rate, gallons per hour 3-9 7-21 15-45Heat output, B.t.u. per hour (MM)... 0. 4-1. 3 1. -2. 9 2. 1-6. 3

Note, in all instances, the diameter of the opening in the front plateis about one-half the diameter of the cylinder. This appears to be oneof the more important characteristics of our invention. If the frontopening is too large, smoking occurs, and if it is too small, puffing ornoisy sputtering occurs.

We claim:

1. An oil burner comprising:

a cylindrical combustion chamber having an internal cylindrical surfacedefining a passageway through said chamber, said passageway terminatingat one end as an air inlet and at the other end as an air outlet in theform of a restrictive circular opening;

said chamber having predetermined dimensions such that the ratio ofchamber diameter to chamber length to opening diameter is about 222-321,preferably about 2:2.5: 1;

means for moving air through the passageway, including:

a. means for directing some of the moving air towards the air outletopening along the center of the passageway and for swirling this air toestablish within the passageway a vortex,

b. means for directing some of the moving air towards the air outletopening along the internal surface of the chamber to establish withinthe passageway a barrier stream which aids in keeping oil off saidsurface, and

c. means "fBFHireEtin'g smae 'artie'anemia t3 the direction of movementof the barrier stream to establish within the passageway a recirculatingair stream;

means for feeding oil into the vortex, whereby the vortex intimatelymixes the oil and air, and the barrier air stream aids in confining thisoil-air mixture to the central portion of the passageway; and

means for igniting the oil-air mixture, whereby the recirculating airstream aids in keeping combustion products within the passageway.

2. The burner defined in claim 1 including insulating means formaintaining the internal surface of said chamber at a temperature inexcess of about 1400 F., preferably within the range of from about l600F. to about 2000 F.

3. An oil burner comprising: a hollow, cylindrical chamber having frontand rear plates; said front plate having therein a centrally located,circular opening which has a diameter equal to from about one-third toabout two-thirds the diameter of the chamber;

said rear plate having therein aperture means adjacent the periphery ofsaid rear plate, and radially extending slit means between the peripheryof the rear plate and the center of the rear plate;

fuel injecting means mounted centrally within said rear plate forspraying oil into said chamber;

means adjacent said rear plate for rapidly moving air through saidaperture means and slit means, into said chamber, and out said opening;

pitched blade means mounted on said rear plate adjacent said slit meansfor causing the air being moved through said chamber to swirl about andmix with the oil being sprayed into said chamber; and

means in said chamber for igniting the oil-air mixture.

4. The burner defined in claim 3 wherein the ratio of chamber diameterto chamber length to opening diameter is about 222-3: 1 preferably about212.5:1.

5. The burner defined in claim 4 wherein the ratio of air entering saidchamber through said aperture means to air entering said chamber throughsaid slit means is about 1:1.

6. The burner defined in claim 5 wherein said chamber is insulated.

7. The burner defined in claim 5 wherein a frustoconical shield,attached to the inside of said rear plate, surrounds said fuel injectingmeans and said igniting means and prevents overheating said fuelinjecting means and igniting means and buildup of carbon and the like onsaid igniting means.

8. The combination comprising:

a revolving fan having a hub and a plurality of vanes extending radiallyfrom said hub;

said vanes forcing air away from the hub and towards the periphery ofthe fan and generating a high velocity air stream which moves away fromthe fan along a line that intersects the plane through which the fanrevolves;

a burner aligned opposite the hub on the same side of the fan as the airstream but out of said air stream, said burner having an air passagewaytherein through which air can pass; and

a plurality of tubular conduits between said burner and fan, each ofsaid conduits having an open end terminating in the air stream andfacing said fan so that air is intercepted and flows into said conduit,and another open end terminating near the air passageway in the burnerso that intercepted air flows through each of said conduits and saidburner.

9. Burner defined in claim 1 wherein the means for feeding oil into thevortex include a plurality of nozzles aligned to direct oil toward thecenter of the chamber, one of said nozzles injecting oil continuouslyand another of said nozzles injecting oil intermittently in response tothermostat control means.

10. Burner defined in claim 9 including means which surrounds said oilfeeding and igniting means and prevents over; heating of said oilfeeding and igniting means and buildup of carbon and the like on saidigniting means.

11. The combination comprising:

a revolving fan having a hub and a plurality of vanes extending radiallyfrom said hub, said vanes forcing air away from the hub toward theperiphery of the fan and generating a high velocity air stream whichmoves away from the fan along a line that intersects the plane throughwhich the fan revolves;

an oil burner aligned opposite the hub on the same side of the fan asthe air stream but out of said air stream, said burner including:

a. a cylindrical combustion chamber having an internal cylindricalsurface defining an air passageway through b. means coupled to saidchamber for directing some air which moves through the passageway towardthe air outlet opening along the center of the passageway and forswirling this air to establish within the passageway a vortex,

c. means coupled to said chamber for directing some of the air whichmoves through the passageway toward the air outlet opening along theinternal surface of the chamber to establish within said passageway abarrier stream which aids in keeping oil off said surface,

d. means coupled to said chamber for directing some of the air whichmoves through the passageway counter to the direction of movement of thebarrier stream to establish within the passageway a recirculating airstream,

e. means for feeding oil into the vortex, whereby the vortex intimatelymixes the oil and air, and the barrier stream aids in confining this oii-air mixture through the central portion of the passageway, and

means for igniting the oil-air mixture, whereby the recirculating airstream aids in keeping combustion products within the passageway; and

a plurality of conduits between said burner and fan, each of saidconduits having an open end terminating in the air stream and facingsaid fan so that air is interceptedand flows into each of said conduits,and another open end terminating near the air inlet end of saidpassageway so that intercepted air flows through each of said conduitsand into said burner to supply air combustion.

12. A combination comprising: fan means for generating a high velocityair stream; oil burner means located at a position outside said airstream, said oil burner comprising:

a. a hollow, cylindrical chamber having front and rear plates,

b. said front plate having therein a centrally located, circular openingwhich has a diameter equal to from about one-third and two-thirds thediameter of the chamber,

c. said rear plate having therein aperture means adjacent the peripheryof said rear plate, and radially extending slit means between theperiphery of the rear plate and the center of the rear plate,

. fuel injecting means mounted centrally within said rear plate forspraying oil into said chamber,

. pitched blade means mounted on said rear plate adjacent said slitmeans for causing the air being moved through said chamber to swirlabout and mix with the oil being sprayed into said chamber, and

. means in said chamber for igniting the oil-air mixture; and meanswhich intercept a portion of the air stream and direct this air streamtoward the rear plate of the burner so that the intercepted air is blownthrough the burner to provide the air of combustion.

1. An oil burner comprising: a cylindrical combustion chamber having aninternal cylindrical surface defining a passageway through said chamber,said passageway terminating at one end as an air iNlet and at the otherend as an air outlet in the form of a restrictive circular opening; saidchamber having predetermined dimensions such that the ratio of chamberdiameter to chamber length to opening diameter is about 2:2-3:1,preferably about 2:2.5:1; means for moving air through the passageway,including: a. means for directing some of the moving air towards the airoutlet opening along the center of the passageway and for swirling thisair to establish within the passageway a vortex, b. means for directingsome of the moving air towards the air outlet opening along the internalsurface of the chamber to establish within the passageway a barrierstream which aids in keeping oil off said surface, and c. means fordirecting some of the air counter to the direction of movement of thebarrier stream to establish within the passageway a recirculating airstream; means for feeding oil into the vortex, whereby the vortexintimately mixes the oil and air, and the barrier air stream aids inconfining this oil-air mixture to the central portion of the passageway;and means for igniting the oil-air mixture, whereby the recirculatingair stream aids in keeping combustion products within the passageway. 2.The burner defined in claim 1 including insulating means for maintainingthe internal surface of said chamber at a temperature in excess of about1400* F., preferably within the range of from about 1600* F. to about2000* F.
 3. An oil burner comprising: a hollow, cylindrical chamberhaving front and rear plates; said front plate having therein acentrally located, circular opening which has a diameter equal to fromabout one-third to about two-thirds the diameter of the chamber; saidrear plate having therein aperture means adjacent the periphery of saidrear plate, and radially extending slit means between the periphery ofthe rear plate and the center of the rear plate; fuel injecting meansmounted centrally within said rear plate for spraying oil into saidchamber; means adjacent said rear plate for rapidly moving air throughsaid aperture means and slit means, into said chamber, and out saidopening; pitched blade means mounted on said rear plate adjacent saidslit means for causing the air being moved through said chamber to swirlabout and mix with the oil being sprayed into said chamber; and means insaid chamber for igniting the oil-air mixture.
 4. The burner defined inclaim 3 wherein the ratio of chamber diameter to chamber length toopening diameter is about 2:2-3:1, preferably about 2:2.5:1.
 5. Theburner defined in claim 4 wherein the ratio of air entering said chamberthrough said aperture means to air entering said chamber through saidslit means is about 1:1.
 6. The burner defined in claim 5 wherein saidchamber is insulated.
 7. The burner defined in claim 5 wherein afrustoconical shield, attached to the inside of said rear plate,surrounds said fuel injecting means and said igniting means and preventsoverheating said fuel injecting means and igniting means and buildup ofcarbon and the like on said igniting means.
 8. The combinationcomprising: a revolving fan having a hub and a plurality of vanesextending radially from said hub; said vanes forcing air away from thehub and towards the periphery of the fan and generating a high velocityair stream which moves away from the fan along a line that intersectsthe plane through which the fan revolves; a burner aligned opposite thehub on the same side of the fan as the air stream but out of said airstream, said burner having an air passageway therein through which aircan pass; and a plurality of tubular conduits between said burner andfan, each of said conduits having an open end terminating in the airstream and facing said fan so that air is intercepted and flows intosaid conduit, and another open end terminating near the air passagewAyin the burner so that intercepted air flows through each of saidconduits and said burner.
 9. Burner defined in claim 1 wherein the meansfor feeding oil into the vortex include a plurality of nozzles alignedto direct oil toward the center of the chamber, one of said nozzlesinjecting oil continuously and another of said nozzles injecting oilintermittently in response to thermostat control means.
 10. Burnerdefined in claim 9 including means which surrounds said oil feeding andigniting means and prevents overheating of said oil feeding and ignitingmeans and buildup of carbon and the like on said igniting means.
 11. Thecombination comprising: a revolving fan having a hub and a plurality ofvanes extending radially from said hub, said vanes forcing air away fromthe hub toward the periphery of the fan and generating a high velocityair stream which moves away from the fan along a line that intersectsthe plane through which the fan revolves; an oil burner aligned oppositethe hub on the same side of the fan as the air stream but out of saidair stream, said burner including: a. a cylindrical combustion chamberhaving an internal cylindrical surface defining an air passagewaythrough said chamber, said passageway terminating as an open end nearthe hub as an air inlet and at the other end as an air outlet in theform of a restrictive circular opening, said chamber havingpredetermined dimensions such that the ratio of chamber diameter tochamber length to opening diameter is 2:2-3:1, b. means coupled to saidchamber for directing some air which moves through the passageway towardthe air outlet opening along the center of the passageway and forswirling this air to establish within the passageway a vortex, c. meanscoupled to said chamber for directing some of the air which movesthrough the passageway toward the air outlet opening along the internalsurface of the chamber to establish within said passageway a barrierstream which aids in keeping oil off said surface, d. means coupled tosaid chamber for directing some of the air which moves through thepassageway counter to the direction of movement of the barrier stream toestablish within the passageway a recirculating air stream, e. means forfeeding oil into the vortex, whereby the vortex intimately mixes the oiland air, and the barrier stream aids in confining this oil-air mixturethrough the central portion of the passageway, and f. means for ignitingthe oil-air mixture, whereby the recirculating air stream aids inkeeping combustion products within the passageway; and a plurality ofconduits between said burner and fan, each of said conduits having anopen end terminating in the air stream and facing said fan so that airis intercepted and flows into each of said conduits, and another openend terminating near the air inlet end of said passageway so thatintercepted air flows through each of said conduits and into said burnerto supply air combustion.
 12. A combination comprising: fan means forgenerating a high velocity air stream; oil burner means located at aposition outside said air stream, said oil burner comprising: a. ahollow, cylindrical chamber having front and rear plates, b. said frontplate having therein a centrally located, circular opening which has adiameter equal to from about one-third and two-thirds the diameter ofthe chamber, c. said rear plate having therein aperture means adjacentthe periphery of said rear plate, and radially extending slit meansbetween the periphery of the rear plate and the center of the rearplate, d. fuel injecting means mounted centrally within said rear platefor spraying oil into said chamber, e. pitched blade means mounted onsaid rear plate adjacent said slit means for causing the air being movedthrough said chamber to swirl about and mix with the oil being sprayedinto said chamber, and f. means in said chamber for igniting the oil-airmixture; and meAns which intercept a portion of the air stream anddirect this air stream toward the rear plate of the burner so that theintercepted air is blown through the burner to provide the air ofcombustion.